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Author Topic: Looking for resonant speaker plans/tips  (Read 1566 times)
W4TQI
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Posts: 8


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« on: September 14, 2003, 10:57:23 PM »

I am interested in constructing a resonant speaker for use with CW.  Unfortunately, all of the web pages I have found on the subject either require hard-to-find specialized parts for the resonant cavity, or have instructions which I have not been able to decipher.

If anyone has information on constructing one of these tuned speakers, I would greatly appreciate it if they could share them with me.

Thanks for your assistance.

-- Patrick
   W4TQI
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K5CEY
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Posts: 217




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« Reply #1 on: September 15, 2003, 01:56:03 AM »

Patrick, I think I understand your logic, however, I feel that the usual approach is to do all the audio shaping and filtering within your equipment. Then the 'speaker simply reproduces what you feed into it.

In the old days, it was common to tune the headphones with a parallel capacitor to a given AF frequency for CW work.

Nowdays with the superlative selectivity offered in the IF section of most receivers, additional audio selectivity is just simply not required.

                      John   K5CEY

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W4TQI
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« Reply #2 on: September 15, 2003, 10:39:33 AM »

[ quote ]
the usual approach is to do all the audio shaping and filtering within your equipment.
  [ snip! ]
Nowdays with the superlative selectivity offered in the IF section of most receivers, additional audio selectivity is just simply not required.
[ /quote ]

I understand this, but a few dollars' worth of PVC pipe for a resonant speaker is more in line with my student's budget than a $170 filter module for my IC-718.  

Additionally, since the IC-718 only has one filter slot, when I _do_ decide to go for a filter module later, I can get an SSB unit, and further narrow the response with the speaker.

Thanks for the words of advice, though.

-- Patrick
   W4TQI
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WB2WIK
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« Reply #3 on: September 18, 2003, 01:09:48 PM »

Golly, there used to be a commercially manufactured speaker (years ago) specifically made for single-frequency CW reproduction, and it was acoustically tuned and quite inexpensive.  Can't remember the name of the manufacturer, but possibly someone reading this will.

The problem with that solution, of course, is that it doesn't lend itself well to a variety of users with different pitch preferences.  If the speaker is sharply tuned to, say, 500 Hz, and the operator can't stand listening to that tone and would much prefer to listen to 400 Hz or 600 Hz, he might be out of luck.

As such, electronically tuned audio filters which perform essentially the same function but using inexpensive electronic circuitry instead of acoustic tuning, are much nicer!  And not expensive at all...can be built for about $10~$15 (not including a fancy enclosure, which really isn't needed).  Advantage is that the sharp "peak" can be user-selected, and the filter can be used with any speaker, or with headphones.

WB2WIK/6
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WA7CC
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« Reply #4 on: October 05, 2003, 06:42:52 PM »

Did you find http://www.qsl.net/kd7rem/resospkr.htm

I heard a resonant speaker recently at a ham fest and I was impressed.
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AK2A
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Posts: 16




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« Reply #5 on: October 13, 2003, 07:04:24 PM »

A quick and easy way to this end is a five inch alarm speaker. They have a passband and they are as efficient a speaker as you will find. Experiment.
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